Van Bentum Prijs: Haroen Zakhimi (Technische Universiteit Eindhoven) - Direct Strength Method for Interacting Loads- Combined Bending and Web Crippling of FirstGeneration Trapezoidal Steel Sheeting

The latest version of the North American specification (AISI-s100-16) allows DSM to be used for determining nominal (pure) axial, flexural and shear strength capacities of cold-formed members. However, the traditional interaction rule is still necessary to account for the combined presence of actions. This is a so-called modular approach; in which actions are first evaluated separately and then the interaction rule accounts for their combined presence.

The contribution of this research was to investigate the feasibility of an integrated (no interaction rule) DSM approach for combined actions; specifically combined bending and web crippling of first-generation trapezoidal steel sheeting. Finite element models were developed to generate the required data. Set-up of these models and their subsequent verification were largely based on experiments on sheet sections subjected to combined bending and web crippling. Both the integrated and modular approach were evaluated by their correlation of strength capacity to the results of the finite element analysis. It is concluded that the modular approach is still superior to the integrated approach. Future research should closely investigate the influence of the elastic buckling solutions and the defined yield loads on the calibrated DSM equations.

Traditional design rules for steel sheeting subjected to combined bending and web crippling (effective width method for bending, empirically derived formulae for web crippling and the interaction rule) are increasingly inept due to mainly two reasons. First, the effective width method discourages cross-section optimization (determining effective widths of complex cross-sections is too laborious) which results in unsustainable use of material. Second, the use of empirically derived formulae for web crippling and the use of the interaction rule do not give insight to the structural engineer. The goal of this research is to move one step forward towards a possible solution for this problem by further developing the DSM so that it may lead to an integral and straight-forward simplified method.

Het oordeel van de jury:
Deze prijs is specifiek bedoeld voor innovatieve toepassingen van (dunne) staalplaat. De Direct Strength Method (DSM) is een nieuwe methode waarmee de uiterste sterkte van dunwandige staal profielen kan worden bepaald op basis van vloeiwaarden en knik/plooi waarden (stabiliteit). Tot op heden is de DSM alleen toepasbaar voor geïsoleerde belastinggevallen. In dit onderzoek is gekeken naar de implementatie mogelijkheden van de DSM voor gecombineerde belastinggevallen; interactie van buigend moment en lijfkreuk voor trapezium staalplaten. De conclusie is dat de nieuwe methode nog geen betere resultaten geeft dan de modulaire methode. De jury heeft de prijs toegekend aan dit onderzoek omdat het een bijdrage levert aan de verbetering van de rekenmethodiek voor constructieve toepassingen van veel gebruikt dunwandig koudgewalst staal. Het onderzoek is goed en degelijk uitgevoerd. ‘Indrukwekkend technisch rekenwerk’, ‘nuttige bijdrage aan de praktijk’, Van-Bentumprijswaardig!

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